An electric motor of this kind comprises a stator having a stator housing, a drive shaft which is rotatable with respect to the stator about an axis of rotation, a rotor which is mounted on the drive shaft and comprises at least one rotor winding, and a commutator mounted on the drive shaft for supplying an electric current to the at least one rotor winding of the rotor during operation of the electric motor. On the stator housing, at least two brushes are mounted which are in sliding contact with the commutator for supplying the electric current to the at least one rotor winding during operation of the electric motor.
An electric motor of this kind is for example known from EP 0 918 996 B1.
In such electric motors, during assembly the brushes mounted on the stator housing must be brought into sliding contact with the commutator mounted on the drive shaft. Typically, such brushes are mounted on the stator housing in a pre-tensioned manner, for example by using spring elements such that, in an assembled state of the electric motor, the brushes are radially pushed against the commutator in an elastic manner. For assembly, however, this means that the brushes must be radially displaced outwards such that the commutator can be inserted between the brushes for bringing the brushes into radial contact with an outer cylindrical surface of the commutator.
Conventionally, for radially displacing the brushes during assembly, a specific tool is used which pushes the brushes radially outwards and holds the brushes in a radially displaced position such that the commutator can be inserted in an assembly direction pointing along the axis of rotation between the brushes. This, however, may complicate the assembly and may lead to additional working steps during assembly.
Hence, EP 0 918 996 B1 proposes to place a magnetic rotor body on the drive shaft in front of the commutator, the magnetic rotor body having an incline which is designed such that the brushes are pushed apart from one another when a brush holder is pushed onto the drive shaft during the assembly process.
A possible drawback herein may be that the forming of the magnetic rotor body with an incline may increase costs in the production of the magnetic rotor body.